Many types of carriages or carts are used to move goods around a work area. To control the movement of the carts, steerable castor wheels are usually used for at least two of the wheels. Castor wheels are mounted to the frame of the cart or carriage to allow them to pivot about a vertical axis. The pivot axis is offset from the horizontal rotational axis of the wheel. This arrangement allows the castor wheel to always be aligned with the direction of movement of the cart.
In some circumstances it is desired to guide carts along tracks. These tracks are usually U-shaped channel members having two spaced-apart sides which guide the wheels. However, if the direction of movement of the cart is reversed while the wheels are within the track, the castor wheels try to pivot about their pivot axes in response to the reversal of direction. The sides of the tracks are usually spaced too closely to allow the wheels to pivot 180.degree.. This causes wheels to drag along the upright sides of the track after such reversal of direction to impede the cart's movement.